In the field of digital imaging, it is desirable to capture complete visual information on three-dimensional objects. As used herein, “complete image data” or a “complete set of image data” refers to a set of images of a target object in which each visible point on the object is represented in at least one of the images. Complete image data for three-dimensional objects may be used, for example, in engineering systems, such as computer-aided design (CAD) systems, to create a representation of a three-dimensional target object. Methods are known for obtaining three-dimensional data for an object. For example, digital cameras may use range-finding methods to capture distance and other metric information for a target object relative to a chosen coordinate system.
To obtain image data for multiple sides of the target object, existing systems capture multiple images of the target object from different perspectives. In one use, a hand-held digital camera may allow the user to manually capture images from a variety of perspectives while walking around the target object. Methods, such as stitching algorithms, are known for combining the image data retrieved from multiple images from different perspectives. The images from different perspectives include common, or overlapping, features. In this regard, three-dimensional image capturing methods are analogous to do-it-yourself methods of creating a panoramic view from multiple separate photographs using a film-based camera. The photographer would try to ensure that similar items appear in adjacent pictures so that the photographs can be aligned with each other to create the final image.
In order to capture a complete set of three-dimensional image data for a target object, it is necessary to capture the image from several available perspectives. For a simple object, such as a ball resting on a table, it is relatively simple task to capture sufficient image data to recreate the three-dimensional image. Images from only a few different perspectives may suffice to capture all of the image data. More complex objects present additional challenges. Various parts of the object may be hidden from many views, and it may be necessary to obtain more images from more perspectives in order to create a complete set of image data. For example, an object with a cavity may be difficult or impossible to fully capture if the camera cannot capture images inside the cavity.
Existing camera systems do not provide a way of determining when the complete image data has been captured. This is particularly a problem when capturing three-dimensional image data for a very large object, such as a building or other structure. A portable camera may be used to capture images of the building in the field. A computer system, separate from the portable camera, may be used to combine the images to create three-dimensional image data. For example, the computer system may be located in an engineering lab, and the camera may download the data for each of the images into the computer system after the user returns to the lab. A problem occurs when the user returns to the lab and downloads the image data, only to discover that the camera did not capture sufficient images to completely represent the object. This wastes the user's time, because it requires the user to determine which additional perspectives are required to create the complete three-dimensional image data and to then return to the target object to capture additional images from the missing perspectives to complete the project. There exists a need to determine when sufficient image data has been captured to create complete three-dimensional image representations.